Technical question; HP-41CV logic PCA


Pictured above is the Logic PCA from a fullnut HP41-CV circa 1984. I have the manual for the HP-41C of which there are similarities. However I am trying to identify specific chips.


ILE 907
ILE 908

ILE 704
ILE 705




Do I have A, B, and C correct?

Cheers, Geoff

edited to correct the CX reference .

Edited: 19 July 2009, 8:42 p.m. after one or more responses were posted


B are the data storage (RAM) devices. Everything else is correct.



Thanks Monte!


My pleasure.

I've been staring at (and carefully measuring dimensions) of
exactly this board for a couple of weeks. It's a marvel of
miniaturization given the technology of the day. I especially
like the capacitors mounted sideways, and on later versions the
stacked 8-pin DIPs.

Trying to squeeze an FPGA, a CPLD, a Flash memory and a static
RAM, plus power supply and voltage translation circuitry on a
board with these physical dimensions is "an interesting
intellectual exercise" to say the least. Finding capacitors
and an inductor that met the height restriction was a royal



That is not a CX board, it is a either a C or CV as the board part number (on opposite this view) is 5081-5563.

There were a total of six different board layouts used in the life cycle of the 41, this was the fifth variant. The next board in sequence was 5081-5564 which was the only CX capable board. It was also used for the C and CV variants by installing the corresponding ROM and D/S parts. The CX added the timer IC 1LF6-0001.


Got my photos mixed up! I was working on a CX halfnut board when I typed the posting and I meant to say CV but CX was stuck in my head, REALLY ;-)

Thanks Randy,

Cheers, Geoff

Edited: 19 July 2009, 8:43 p.m.


Hi Geoff,

Diego Diaz has a nice page showing the successive CPU boards on his Clonix-41 website

This can be helpful identifying boards & components.



Edited: 20 July 2009, 12:48 a.m.


There are no coincidences,

I was just on my way to Deigos site to copy his I/O-assembly flex-PCB pad instructions and thought to visit here first.

So coincidence? off to Deigos,

Cheers, Geoff

The only manual I have is of the original HP-41C with screwed down logic PCA.


FYI, the RAYT8306 line on the ceramic chip C is the vendor and date code, not the part number. The part number is the on first line, probably 1820-0953. The -1 suffix is most likely a minor manufacturing variation such as the case type, as any significant functional change would have resulted in a new part number assignment. Earlier 41s used the 1820-0566.


The 1820-0953 replaced the original 1820-0566. The new part eliminated two resistors, R2 (100k) and R3 (1m) which were moved onto the die. The parts are otherwise interchangeable, so long as the resistor issue is addressed with the swap.


digging up my hp 41C service manual and digging through the PCAs I have.

Eric, some of us have bad eyesight and I thought the brand name would be easier to see as opposed to the discriptive label.

Thanks for the help.

Cheers, Geoff


Eric, some of us have bad eyesight

I'm one of 'em.

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